The present disclosure relates to a signal processing arrangement, to a sensor arrangement with such signal processing arrangement and to a signal processing method, each processing a signal from a capacitive sensor.
Sensors with capacitive properties are widely used. For example, many micro electro mechanical systems, MEMS, sensors, like MEMS microphones, have a varying capacitance depending on the value to be sensed.
MEMS microphones are an example of a capacitive sensor application where a very high input dynamic range needs to be supported. The signal of the capacitive sensor may have peak values at the input that might even exceed the supply rails of an associated signal processing circuit. For example, such a signal may need to be compressed to fit within the signal swing given a limited supply voltage of a first amplifier of the signal processing circuit. Due to the strict noise requirements and usually small sensor capacitances, a conversion of the signal into a charge domain or current domain is usually not possible. One option is to compress the signal directly at the input pin of the first amplifier into the supply range, before it gets into an active circuitry, where clipping may happen.
To compress the signal is challenging, as the signal information may get distorted by the compression. For example, in conventional approaches, the signal may be attenuated or clipped directly at the input pin, in case it exceeds the input range.